Posted Mon, 20 Apr 2015 10:16:33 GMT by Anne Hansen

I have seen some old posts where a link is given to a demo video on how to apply evapotranspiration in a Feflow model. But I cannot find the video using that link anymore.
Has the video been moved to a new location?

Best regards,

Posted Tue, 21 Apr 2015 09:33:56 GMT by Denim Umeshkumar Anajwala
Dear Anne,

The respective video was based on FEFLOW 5.x and therefore is no longer useful nowadays. Do you have a specfic question about the assignment?

Best regards,
Posted Fri, 24 Apr 2015 06:53:39 GMT by Anne Hansen
Dear Peter,

Thank you for your answer. I just wanted to have an idea of how to apply evapotranspiration on a model setup. Is it just to apply a fluid-flux BC on the nodes in fx. the upper 1 m of the domain and then use the equation editor to define how the flux depends on fx. the model calculated saturation?

Best regards,
Posted Mon, 27 Apr 2015 08:26:33 GMT by Carlos Andres Rivera Villarreyes Global Product Specialist - FEFLOW
Dear Anne,
If you would like to apply an expression for the outflow flux, you can only do it by means of a material property named "Sink/Source" (or Inflow/Outflow on top/bottom for 3D models). If the model is transient for flow, you can simply make a right-click on the parameter name and activate the expression editor. In such a manner, the fluid-flux BC is free for other purposes such as recharge.
Posted Fri, 15 May 2015 00:23:30 GMT by
Unfortunately, Carlos is correct. Version 6, and earlier versions of FEFLOW, allow a "parameter expression" on elemental properties only, two of which are actually boundary conditions (in/outflow on top/bottom and source/sink). Recharge could be used to simulate ET if your model can be set up to simulate ET (negative recharge) only in layer one. Otherwise, you would have to use the source/sink "material" but this is further complicated by its odd units: your parameter expression would have to account for the control volume associated with this "material" (which could be specified and accessed via an elemental user data distribution).

I once tried doing something similar using a parameter expression on source/sink and it did not work so well, which leads me to think that simulating ET this way might not work so well except in simple cases.

There are no "parameter expressions" available for "Boundary Conditions (BC)"

Another solution, which would probably work well, would be to program an IFM module to handle ET using flux or well nodes (well nodes would be easiest). Let me know if you want help with such an approach.

I think the ET video would still be applicable, but the URL is broken and has not been fixed.

Posted Tue, 19 May 2015 15:08:52 GMT by Denim Umeshkumar Anajwala
Here's the old video. The swf file in the zip archive can be opened by any web browser.
Posted Wed, 20 May 2015 13:09:59 GMT by Anne Hansen
Thank you Carlos and Pete for your answers, and to Peter for the video. I will have a look at it and see if I can get one of your suggestions to work. If not I will get back to you.

Posted Fri, 03 Aug 2018 17:15:18 GMT by Barbara Tsuyuguchi Civil Engineer Student

I am trying to calculate the evapotranspiration from a shallow aquifer, but I am not getting good results.

As a first attempt, I am applying a linear function using the "Expression editor" in "inflow/outflow on top/bottom" to consider water depth. In order to do this, the outflow function is conditioned to "Hydraulic Head" and "Elevation Information".

Do you have some tutorial or video that can help me to deal with it? Or some example file?

Unfortunately, the video from preview version didn't help me that much. 

Best regards,
Posted Tue, 07 Aug 2018 10:44:15 GMT by Björn Kaiser
Could you please provide the mathematical dependencies by means of an equation? If the math you are interested in is clear for me, I may assist you with a workflow.
Posted Thu, 09 Aug 2018 13:46:13 GMT by Barbara Tsuyuguchi Civil Engineer Student
Dear Björn Kaiser,

thank you for your support.

The expression used is presented in the picture attached.

where 2.64 mm/day is the evapotranspiration rate when the water table is reaching the top of the aquifer/surface, and considering that evapotranspiration process acts over the aquifer only until the 2 m water depth (from the top of the aquifer/surface).

If I wasn't clear enough, please, let me know.

Best regards,

Best regards,

Posted Tue, 14 Aug 2018 11:09:35 GMT by Björn Kaiser
You need to address the nodes of the first slice. Under the assumption that the head located at Slice 1 represents the water level you may implement the attached schematic expression in your more complex expression. Please also note the units in the Expression Editor.
Posted Tue, 11 Sep 2018 14:55:12 GMT by Barbara Tsuyuguchi Civil Engineer Student
Dear Björn Kaiser,

I didn't understand the expression into brackets. I read about the meaning of nodes parameters you used, but I couldn't understand how this expression address the nodes of the first slice. Could you help us?

Best regards,
Posted Wed, 26 Sep 2018 12:33:51 GMT by Christian Helweg Senior groundwater specialist
I believe that the bracket refers to an if, then ...else sentence. In feflow expression builder you can select "if" and it gives you the structure.

Posted Wed, 26 Dec 2018 19:18:59 GMT by Barbara Tsuyuguchi Civil Engineer Student

I am still having some difficulties to calculate evapotranspiration in my model, and I would appreciate a lot if someone could help me with this issue.

For calculating evaporation, if I am using an expression that depends of water level, when simulation is running, does  the software recalculate the evaporation rate each time step using the current water level information? I am implementing it using an expression on In/outflow on top/bottom, but it seems it considers only the initial water level for the whole period. How can I fix it?

Posted Tue, 08 Jan 2019 12:34:32 GMT by Peter Schätzl
There are two ways of applying an expression. One is for calculating a time-constant parameter (in the Editor toolbar), the other one for applying an expression at run-time. The latter can be found via the context menu of the corresponding parameter (In/outflow on top/bottom) in the Data panel.
Please note that during the simulation as well as in the DAC file currently the calculated and applied parameter values are not visible in the view.
Best regards,
Posted Wed, 16 Jan 2019 00:33:26 GMT by Barbara Tsuyuguchi Civil Engineer Student
Hi Peter,

thank you very much for your answer. It was very helpful!!

I noted what you said about the values not being visible, but just to be sure, there isn't any way to access the calculated parameter values (In/outflow on top/bottom) for each time step?
Posted Thu, 19 Dec 2019 04:53:29 GMT by Razi Sadath P V Senior Research Fellow
If I used In/outflow for evaporation, how can I assign recharge??

You must be signed in to post in this forum.